U.S. patent application number 13/187663 was filed with the patent office on 2012-05-31 for ratcheting mechanical torque wrench with an electronic sensor and display device.
Invention is credited to Muniswamappa Anjanappa, Xia Chen.
Application Number | 20120132043 13/187663 |
Document ID | / |
Family ID | 46125744 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120132043 |
Kind Code |
A1 |
Chen; Xia ; et al. |
May 31, 2012 |
RATCHETING MECHANICAL TORQUE WRENCH WITH AN ELECTRONIC SENSOR AND
DISPLAY DEVICE
Abstract
A mechanical torque wrench for engaging a workpiece, including a
wrench body, a wrench head with a workpiece engaging portion and a
bar, the wrench head being pivotably secured to the wrench body, a
set spring, a pawl disposed between the bar and the set spring, and
a dial screw, wherein rotation of the dial screw in a first
direction compresses the set spring. A resistive element is coupled
to the dial screw and produces an output signal. A first sensor
produces a first output signal that is proportional to an amount of
rotation of the mechanical torque wrench. A processor converts the
resistive element output signal into an equivalent torque value
indicating a preset torque to be applied by and converts the first
output signal into a first angle value. A user interface includes a
display for displaying the equivalent torque value. The application
of a torque greater than the preset torque causes the wrench head
to pivot relative to the wrench body.
Inventors: |
Chen; Xia; (Clarksville,
MD) ; Anjanappa; Muniswamappa; (Ellicott City,
MD) |
Family ID: |
46125744 |
Appl. No.: |
13/187663 |
Filed: |
July 21, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61417930 |
Nov 30, 2010 |
|
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Current U.S.
Class: |
81/479 |
Current CPC
Class: |
B25B 23/1425
20130101 |
Class at
Publication: |
81/479 |
International
Class: |
B25B 23/144 20060101
B25B023/144 |
Claims
1. A mechanical torque wrench for engaging a workpiece, comprising:
a wrench body defining an elongated interior compartment; a wrench
head including a workpiece engaging portion and a bar extending
therefrom, the wrench head being pivotably secured to a first end
of the wrench body at a pivot joint, the bar extending into the
interior compartment and the workpiece engaging portion extending
outwardly from the wrench body; a set spring disposed within the
interior compartment of the wrench body; a block disposed between a
rear face of the bar and the set spring; a dial screw threadably
received within the interior compartment of the wrench body such
that the dial screw moves along a longitudinal axis of the wrench
body when rotated, rotation of the dial screw in a first direction
compressing the set spring and rotation in a second direction
allowing expansion of the set spring; a resistive element
operatively coupled to the dial screw and producing an output
signal, the output signal being dependent on a position of the dial
screw relative to the resistive element; a first sensor operatively
coupled to the wrench body and producing a first output signal, the
first output signal being proportional to an amount of angular
rotation being applied to the workpiece by the torque wrench during
a first rotational cycle of the mechanical torque wrench; a
processor for converting the output signal into an equivalent
torque value, the equivalent torque value indicating a preset
torque to be applied by the mechanical torque wrench to the
workpiece, and converting the first output signal into a first
angle value through which the workpiece has been rotated; and a
user interface including a display for displaying the equivalent
torque value, wherein application of a torque greater than the
preset torque to the workpiece causes the wrench head to pivot
relative to the wrench body about the pivot joint.
2. The mechanical torque wrench of claim 1, further comprising a
hand grip located on a second end of the wrench body, and a set
ring positioned adjacent the hand grip, the set ring being
operatively connected to the dial screw and rotatable relative to
the wrench body.
3. The mechanical torque wrench of claim 2, the resistive element
further comprising a potentiometer fixed to the interior
compartment of the wrench body.
4. The mechanical torque wrench of claim 3, the potentiometer
further comprising a sliding potentiometer including a resistor and
a wiper assembly, wherein movement of the dial screw along the
longitudinal axis of the wrench body similarly moves the wiper
assembly along the resistor such that the output signal is
altered.
5. The mechanical torque wrench of claim 1, further comprising a
ratchet mechanism so that torque can be applied to the workpiece
using multiple rotational cycles of the electronic torque wrench
without having to disengage the workpiece.
6. The mechanical torque wrench of claim 5, wherein the processor
determines the first angle value during the first rotational cycle,
and converts a second output signal produced by the first sensor
during a second rotational cycle into a second angle value through
which the workpiece has been rotated.
7. The mechanical torque wrench of claim 6, wherein the processor
adds the first angle value and the second angle value to determine
an accumulated angle value.
8. The mechanical torque wrench of claim 1, the first sensor
further comprising a gyroscopic sensor for indicating the amount of
angular rotation applied to the workpiece.
9. A mechanical torque wrench for engaging a workpiece comprising:
a wrench body defining an elongated interior compartment; a wrench
head pivotably received in the interior compartment, the wrench
head including a drive portion for engaging the workpiece and a bar
extending into the interior compartment; a set spring disposed
within the interior compartment of the wrench body; a dial screw
rotatably received within the interior compartment of the wrench
body, rotation of the dial screw in a first direction increasing
force exerted on the set spring and rotation of the dial screw in a
second direction decreasing force exerted on the set spring by the
dial screw; a gyroscopic sensor operatively coupled to the wrench
body and producing a first output signal, the first output signal
being proportional to an amount of angular rotation being applied
to the workpiece by the torque wrench; a processor for converting
the first output signal into a first angle value through which the
workpiece has been rotated during a first rotational cycle of the
torque wrench; and a user interface including a display for
displaying the first angle value, wherein application of a torque
greater than a preset torque value to the workpiece causes the
wrench head to pivot relative to the wrench body.
10. The mechanical torque wrench of claim 9, further comprising a
resistive element including a resistor and a wiper assembly, the
wiper assembly being operatively coupled to the dial screw, the
resistive element producing an output signal that is related to a
position of the dial screw relative to the resistive element.
11. The mechanical torque wrench of claim 10, wherein the output
signal of the resistive element is proportional to the preset
torque value.
12. The mechanical torque wrench of claim 9, further comprising a
ratcheting mechanism so that torque can be applied to the workpiece
using multiple rotational cycles of the torque wrench.
13. The mechanical torque wrench of claim 12, wherein the processor
converts a second output signal of a second rotational cycle into a
second angle value through which the workpiece has been rotated
during second rotational cycle.
14. The mechanical torque wrench of claim 13, wherein the processor
adds the first angle value and the second angle value to determine
an accumulated angle value.
Description
CLAIM OF PRIORITY
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/417,930 filed Nov. 30, 2010, the entire
disclosure of which is incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to mechanical torque
wrenches. More particularly, the present invention relates to a
ratcheting mechanical clicker type torque wrench and a sensor for
determining an amount of angular rotation of the torque wrench.
BACKGROUND OF THE INVENTION
[0003] Often, fasteners used to assemble performance critical
components are tightened to a specified torque level to introduce a
"pretension" in the fastener. As torque is applied to the head of
the fastener, the fastener may begin to stretch beyond a certain
level of applied torque. The stretching results in pretension in
the fastener which then holds the joint together. Additionally, it
is often necessary to further rotate the fastener through a
specified angle after the desired torque level is applied.
Over-stressing fasteners can lead to their failure whereas
under-stressing can lead to joint failure, leakage, etc.
Furthermore, in situations where gaskets are being utilized between
the components being joined, an unequally stressed set of fasteners
can result in gasket distortion and subsequent problems like
leakage. Accurate and reliable torque wrenches help insure that
fasteners are tightened to the proper specifications.
[0004] Torque wrenches may be of the mechanical or electronic type.
Mechanical torque wrenches are generally less expensive than
electronic. There are several types of mechanical torque wrenches
that are routinely used to tighten fasteners to specified torque
levels. Of these, clicker type mechanical torque wrenches are very
popular. Clicker type mechanical torque wrenches make an audible
click to let the user know when a preset torque level has been
achieved and simultaneously provide a feeling of sudden torque
release to the user.
[0005] One example of a clicker type torque wrench includes a
hollow tube in which a spring and block mechanism is housed. The
block is forced against one end of a bar that extends from a drive
head. The bar and drive head are pinned to the hollow tube about a
pivot joint and rotate relative thereto once the preset torque
level is exceeded. The preset torque level is selected by a user by
causing the spring to exert either greater or lesser force on the
block. The force acts on the bar through the block to resist the
bar's rotation relative to the hollow tube. As the torque exerted
on the fastener exceeds the preset torque value, the force tending
to cause the bar to pivot relative to the hollow tube exceeds the
force exerted by the block that prevents the bar's rotation, and
the block "trips." When released by the block's action, the bar
pivots and hits the inside of the tube, thereby producing a click
sound and a sudden torque release that is detectable by the
user.
[0006] Another example of a clicker type torque wrench measures the
deflection of a deflectable beam relative to a non-deflectable
beam, the deflectable beam causing a click once the preset torque
is reached. These and other types of clicker type mechanical torque
wrenches are popular since they are relatively easy to operate and
make torquing relatively quick and simple. The user merely sets the
desired torque value and pulls on the handle until he hears and
feels the click and torque release, indicating that the desired
torque value has been reached.
[0007] One drawback that limits the usage of many mechanical type
torque wrenches is the inability to measure the angular rotation of
the fastener. Typically, mechanical torque wrenches lack this
ability because they do not include a power source and, therefore,
cannot support the use of the required sensor, such as a gyroscopic
sensor. As such, for fasteners where it is necessary to rotate the
fastener through a specified angle after the desired torque level
is applied with the mechanical torque wrench, an electronic torque
wrench with the ability to measure angular rotation is often
required to complete tightening the fastener.
[0008] Some electronic torque wrenches (ETWs) are capable of
measuring angular rotation of the wrench, and therefore the
fastener, in addition to measuring the amount of torque applied to
the fastener. As such, for those fasteners that require further
rotation after the initial application of the desired torque value,
an electronic torque wrench may be desirable since only one torque
wrench is required. However, fasteners are often positioned such
that both the torque and the desired additional angular rotation
may not be applied with the torque wrench in a single, continuous
motion. In such cases, an electronic torque wrench having a
ratcheting feature can be used.
[0009] The present invention recognizes and addresses certain or
all the foregoing considerations, and others, of prior art
constructions.
SUMMARY OF THE INVENTION
[0010] One embodiment of the present invention provides a
mechanical torque wrench with a wrench body defining an elongated
interior compartment, a wrench head including a workpiece engaging
portion and a bar extending therefrom, the wrench head being
pivotably secured to a first end of the wrench body at a pivot
joint, the bar extending into the interior compartment and the
workpiece engaging portion extending outwardly from the wrench
body. A set spring is disposed within the interior compartment of
the wrench body, a block is disposed between a rear face of the bar
and the set spring, and a dial screw is threadably received within
the interior compartment of the wrench body such that the dial
screw moves along a longitudinal axis of the wrench body when
rotated, rotation of the dial screw in a first direction
compressing the set spring and rotation in a second direction
allowing expansion of the set spring. A resistive element is
operatively coupled to the dial screw and produces an output
signal, the output signal being dependent on a position of the dial
screw relative to the resistive element. A first sensor is
operatively coupled to the wrench body and produces a first output
signal, the first output signal being proportional to an amount of
rotation being applied to the workpiece by the torque wrench during
a first rotational cycle of the mechanical torque wrench. A
processor converts the output signal into an equivalent torque
value, the equivalent torque value indicating a preset torque to be
applied by the mechanical torque wrench to the workpiece, and
converting the first output signal into a first angle value through
which the workpiece has been rotated. A user interface includes a
display for displaying the equivalent torque value. The application
of a torque greater than the preset torque to the workpiece causes
the wrench head to pivot relative to the wrench body about the
pivot joint.
[0011] Another embodiment of the present invention provides a
mechanical torque wrench with a wrench body defining an elongated
interior compartment, a wrench head pivotably received in the
interior compartment, the wrench head including a drive portion for
engaging the workpiece and a bar extending into the interior
compartment. A set spring is disposed within the interior
compartment of the wrench body, a dial screw is rotatably received
within the interior compartment of the wrench body, rotation of the
dial screw in a first direction increasing force exerted on the set
spring and rotation of the dial screw in a second direction
decreasing force exerted on the set spring by the dial screw. A
gyroscopic sensor is operatively coupled to the wrench body and
produces a first output signal, the first output signal being
proportional to an amount of rotation being applied to the
workpiece by the torque wrench. A processor converts the first
output signal into a first angle value through which the workpiece
has been rotated during a first rotational cycle of the torque
wrench. A user interface includes a display for displaying the
first angle value. The application of a torque greater than a
preset torque value to the workpiece causes the wrench head to
pivot relative to the wrench body about the pivot joint
[0012] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate one or more
embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth in the specification, which makes
reference to the appended drawings, in which:
[0014] FIG. 1 is a top view of a mechanical clicker type torque
wrench with an electronics unit in accordance with an embodiment of
the present invention;
[0015] FIG. 2 is an exploded perspective view of the mechanical
torque wrench as shown in FIG. 1;
[0016] FIG. 3 is a perspective view of a resistive element assembly
of the mechanical torque wrench as shown in FIG. 1;
[0017] FIG. 4 is an exploded perspective view of the resistive
element assembly of the mechanical torque wrench as shown in FIG.
1;
[0018] FIG. 5 is a partial cut-away top view of the mechanical
torque wrench as shown in FIG. 1;
[0019] FIGS. 6A and 6B are partial cross-sectional views of the
mechanical torque wrench as shown in FIG. 1, revealing the
embodiment of the resistive element assembly shown in FIG. 3;
[0020] FIGS. 7A and 7B are partial cross-sectional views of the
mechanical torque wrench as shown in FIG. 1, revealing an alternate
embodiment of a resistive element assembly;
[0021] FIG. 8 is a partial electrical circuit of the electronics
unit of the mechanical torque wrench as shown in FIG. 1;
[0022] FIG. 9 is a block diagram representation of the electronics
unit of the mechanical torque wrench as shown is FIG. 1;
[0023] FIG. 10 is a block diagram representation of electronics
unit of the mechanical torque wrench as shown in FIG. 1;
[0024] FIG. 11 is a flow chart of the algorithm utilized by the
mechanical torque wrench as shown in FIG. 1 to measure accumulated
angular rotation of the wrench;
[0025] FIGS. 12A, 12B and 12C are views of a display device as used
with the mechanical torque wrench shown in FIG. 1; and
[0026] FIG. 13 is a flow chart of the display algorithm of the
display device as shown in FIGS. 12A, 12B and 12C.
[0027] Repeat use of reference characters in the present
specification and drawings is intended to represent same or
analogous features or elements of the invention according to the
disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Reference will now be made in detail to presently preferred
embodiments of the invention, one or more examples of which are
illustrated in the accompanying drawings. Each example is provided
by way of explanation, not limitation, of the invention. In fact,
it will be apparent to those skilled in the art that modifications
and variations can be made in the present invention without
departing from the scope and spirit thereof. For instance, features
illustrated or described as part of one embodiment may be used on
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0029] Referring now to FIGS. 1 and 2, a preferred embodiment of a
mechanical clicker type torque wrench 10 includes an electronics
unit 12, an elongated wrench body 14, a wrench head 16 including a
ratcheting mechanism 18 and a bar 20 extending therefrom, and a
hand grip 20 attached to one end of wrench body 14. As shown,
ratcheting mechanism 18 of wrench head 16 includes a lever device 7
that allows a user to select whether torque is applied to a
fastener in either a clockwise (CW) or counter-clockwise (CCW)
direction. The ratcheting mechanism 18 includes a boss 9 for
receiving variously sized sockets, extensions, etc.
[0030] Electronics unit 12, including a user interface, is received
on wrench body 14 between the hand grip and wrench head 16. An
interior compartment 19 of wrench body 14 houses a clicker
mechanism 26 that includes a set spring 28, a plug assembly 30, a
block 32, and slender bar 20, as best seen in FIG. 5. The block is
sandwiched between the slender bar and the spring. Additionally, a
gyroscopic sensor 27 is mounted in mechanical torque wrench 10 on
the printed circuit board 42. Gyroscopic sensor 27 is preferably a
MEMS gyroscopic sensor, such as Model No. XV3500 manufactured by
EPSON, Tokyo, Japan. However, other sensors that are capable of
angular measurement may also be used.
[0031] An adjustment assembly 34 is disposed on wrench body 14
opposite wrench head 16 for selectively adjusting a resistive
element assembly 36 mounted to wrench body 14. Adjustment assembly
34 includes an end cap 38, a dial screw 40, and a nut 45 (FIG. 6A)
fixed in interior compartment 19 of wrench body 14. End cap 38
engages a first end 44 of dial screw 40 and is selectively
rotatable relative to wrench body 14. A second end 46 of dial screw
is threaded and engages nut 45 such that rotation of dial screw 40
causes it to move axially along a longitudinal center axis 48 of
wrench body 14. A spring cap 11 is received in the back end of set
spring 28 and receives an engagement spring 13 therein. A thrust
washer 15 abuts the rear end of engagement spring 13 and exerts
force from dial screw 40 on set spring 28 via contact with spring
cap 11 when the engagement spring is fully compressed therein, as
discussed in greater detail below. A ball cam 17 is positioned
between a front face of dial screw 40 and thrust washer 15.
[0032] Wrench head 16 is pivotably secured to a first end of wrench
body 14 such that bar 20 extends into interior compartment 19 and
ratcheting mechanism 18 protrudes outwardly from wrench body 14.
Wrench head 16 is secured to wrench body at pivot joint 50 that
includes a pivot pin 52 that is both perpendicular to longitudinal
center axis 48 of wrench body 14 and transverse to a plane defined
by torque wrench 10 as it is rotated about a workpiece during
torquing operations. As shown, wrench head 16 includes ratchet
mechanism 18 so that torque may be selectively applied to a
workpiece (not shown) in either the clockwise or counterclockwise
direction. However, alternate embodiments need not include a
ratcheting mechanism.
[0033] Electronics unit 12 includes a user interface including a
visual display 54, preferably a liquid crystal display, and a user
input device 56 that includes a bank of buttons. Visual display 54
and input device 56 are both supported on printed circuit board 42
which is in turn supported by a housing 58, preferably formed of
injection molded plastic. Printed circuit board 42 additionally
carries a microcontroller and any additional electronic components
for operation of the electronics unit. Visual display 54 includes a
numerical display 60 (FIGS. 12A through 12C) to assist a user in
setting a preset torque for the torque wrench, a torque unit
indicator 62 that displays the units of the preset torque, and a
battery level indicator 95 for displaying the condition of the
batteries. As shown, input device 56 includes a power button 66a, a
unit selector button 66b for choosing the units to be shown on
visual display 54, an angle mode selector button 66c for entering
the angle measurement mode of the wrench and increment/decrement
buttons 65a and 65b for selecting a target angle, as discussed in
greater detail below. Further, the housing of electronics unit 12
has a flat bottom surface 67 that forms a stable platform for
setting the torque wrench down when it is not in use. The housing
also defines a battery compartment 70 that is external to interior
compartment of wrench body 14.
[0034] Referring now to FIGS. 3 and 4, resistive element assembly
36 includes a resistive element 72a, e.g., a potentiometer, a
housing 74 and an end cap 76. As shown, the resistive element is a
sliding potentiometer that includes a linear resistor 78, a wiper
assembly 80 configured for motion along linear resistor 78, an
adjustment pin 82 extending outwardly from wiper assembly 80 and
terminal leads 84 for receiving wires from electronics unit 12.
Motion of wiper assembly 80 along linear resistor 78 causes the
overall resistance of sliding potentiometer 72a to vary, as
discussed in greater detail below. Sliding potentiometer 72a is
slidably received in a central recess 86 of housing 74. Axial
recesses 88 extending outwardly from central recess 86 slidably
receive axial guides 90 that extend outwardly from sliding
potentiometer 72a to insure proper positioning of the potentiometer
within housing 74. After linear potentiometer 72a is positioned in
housing 74, end cap 76 is secured to housing 74 by inserting
mounting pins 92 extending from end cap 76 into pin apertures 94
formed on housing 74 in a press-fit. End cap 76 includes a lead
aperture 96 that allows wires from electronics unit 12 to pass
therethrough so they may be connected to terminal leads 84 on
sliding potentiometer 72a. Once assembled, resistive element
assembly 36 is mounted in an aperture 98 defined by wrench body 14.
Housing 74 and aperture 98 include corresponding pairs of axially
extending abutment surfaces 99a and 99b, respectively, such that
when housing 74 is mounted in aperture 98, the outer surfaces of
housing 74 and wrench body 14 provide a smooth cylindrical
surface.
[0035] As best seen in FIG. 5, block 32 of clicker mechanism 26 is
substantially cube-shaped and is disposed between a rear face 21 of
bar 20 and a forward face 31 of plug assembly 30. Forward face 31
of the plug assembly includes a recess 31 that is shaped
correspondingly to the outer surface of block 32 which rests
against it. Recessed forward face 31 insures that the vertical
longitudinal center axis of block 32 remains perpendicular to a
plane defined by longitudinal center axis 48 as torque wrench 10 is
rotated. As such, block 32 functions properly when the preset
torque value is reached, as discussed in greater detail below. A
rearward face 33 of plug assembly 30 receives the front end of set
spring 28. Plug assembly 30 has an outer surface dimensioned
sufficiently close to the inner diameter of body 14 (i.e. interior
compartment 19) so that although the plug assembly is slidably
received within interior compartment 19 of wrench body 14, it is
limited to minimal transverse motion relative to wrench body
14.
[0036] Referring now to FIGS. 6A and 6B, end cap 38 of adjustment
assembly 34 is selectively rotatable relative to hand grip 22, and
therefore wrench body 14. End cap 38 includes an annular array of
locking teeth 39 formed about its forward inner perimeter that are
selectively engageable with an annular array of locking teeth 37
formed about the rear outer periphery of hand grip 22. In a forward
position (FIG. 6B) relative to hand grip 22, locking teeth 39 on
end cap 38 engage locking teeth 37 on hand grip 22, thereby
rotationally fixing end cap 38 to wrench body 14. In a rearward
position (FIG. 6A), locking teeth 39 to end cap 38 are disengaged
from locking teeth 37 on hand grip 22 and end cap 38 is therefore
rotatable relative to wrench body 14.
[0037] End cap 38 includes an axial bore 33 that is configured to
slidably receive first end 44 of dial screw 40. As shown, an outer
surface of dial screw first end 44 and an inner surface of axial
bore 33 define corresponding hexagonal cross-sectional shapes such
that end cap 38 is non-rotatable relative to dial screw 40. Second
end 46 of dial screw 40 is threaded and received by correspondingly
threaded nut 45 that is rotationally fixed inside inner compartment
19 of wrench body 14. As such, rotation of end cap 38, and
therefore dial screw 40, relative to wrench body 14 causes dial
screw 40 to translate axially along longitudinal center axis 48 of
wrench body 14. The direction of axial motion is dependent on the
direction of rotation of end cap 38 and causes dial screw 40 to
either increase or decrease the torque value at which block 32
trips.
[0038] As best seen in FIG. 6A, when dial screw 40 is in the fully
retracted position, thrust washer 15 abuts threaded nut 45, and
engagement spring 13 exerts a forward biasing force on set spring
28 through spring cap 11. This forward biasing force insures that
block 32 remains properly positioned between the forward face of
plug assembly 31 and the rear face of slender bar 20 (FIG. 5) when
dial screw 40 is fully retracted. To preset a torque value from the
fully retracted position, end cap 38 is rotated in a clockwise
direction such that dial screw 40 moves forward against set spring
28. In so doing, dial screw 40 urges thrust washer 15 forwardly
until the thrust washer abuts spring cap 11 and engagement spring
13 is fully compressed therein. Continued rotation of end cap 38
causes thrust washer 15 to exert an increasing amount of force on
set spring 28, thereby causing the amount of torque required to
"trip" the torque wrench to similarly increase.
[0039] As shown, an annular groove 41 is formed about a central
portion of dial screw 40 by a pair of radially outwardly extending
shoulders 43a and 43b. Annular groove 41 is configured such that
its fore and aft dimensions are substantially the same as the fore
and aft dimensions of adjustment pin 82 of sliding potentiometer
72a. Annular groove 41 is configured to slidably receive adjustment
pin 82 of sliding potentiometer 72a such that, as dial screw 40 is
rotated in either direction and is translated along longitudinal
center axis 48 of wrench body 14, adjustment pin 82 is engaged and
moved by either radial shoulder 43a or 43b, depending upon the
direction of axial motion of dial screw 40, so that the overall
resistance provided by the sliding potentiometer is altered.
Annular groove 41 is dimensioned and configured such that minimal
friction is encountered as radial shoulders 43a and 43b are rotated
relative to adjustment pin 82, and adjustment pin 82 is configured
to have a smooth cylindrical outer surface. As well, adjustment pin
82 is received in annular groove 41 so as to minimize unwanted
vibrations that can possibly be transferred to the sliding
potentiometer during use. Vibrations are also reduced since dial
screw 40 is threadedly received by nut 45, and thereby immobilized
with respect to the wrench body. These features help to maintain a
stable display of the preset torque value on the display. Alternate
embodiments of dial screw 40 may include an annular groove that
extends radially inwardly into the body of dial screw 40 rather
than being formed by a pair of radial solders 43a and 43b, as
shown.
[0040] Referring now to FIGS. 7A and 7B, an alternate embodiment of
a resistive element and dial screw is shown. The resistive element
is an annular potentiometer 72b including an outer ring 73 that is
rotationally fixed to inner compartment 19 of wrench body 14, an
inner ring 75 that is rotatably secured to outer ring 73, and a
central aperture 77 that is defined by inner ring 75 and configured
to slidably receive a portion of dial screw 40a. As in the
previously discussed embodiment, dial screw 40a includes a first
end 44 having a cross-sectional shape that is complimentary to that
of internal bore 33 of end cap 38, and second end 46 that is
threadedly received in nut 45 that is non-rotatably secured to
interior compartment 19 of wrench body 14. However, rather than the
previously discussed annular groove and adjustment pin arrangement,
dial screw 40a has an extended hexagonally shaped first portion 44
that extends along the length of dial screw 40a such that it is
received in the correspondingly shaped central aperture 77 of inner
ring 75 of the annular potentiometer. As such, as end cap 38 is
rotated relative to hand grip 22, thereby causing axial motion of
dial screw 40a along longitudinal center axis 48 of wrench body 14,
inner ring 75 of the annular potentiometer rotates relative to
outer ring 73. Outer ring 73 includes a resistive element and inner
ring 75 includes a wiper assembly. Rotation of inner ring 75
relative to outer ring 73 causes the overall resistance of annular
potentiometer 72b to change, as previously discussed with respect
to the sliding potentiometer.
[0041] FIG. 8 illustrates a sensor electrical circuit 101 that
determines the selected resistance of either sliding potentiometer
72a or annular potentiometer 72b in order to create an electrical
signal for use by microcontroller 102. Sensor electrical circuit
101 utilizes a fixed DC excitation voltage (Vcc) in the range of 3
to 5 volts. Referring additionally to FIG. 9, sensor electrical
circuit 101 sends an analog electrical signal 60 that varies in
voltage proportionally to the resistance of the potentiometer to a
resistive element signal conditioning unit 62 that amplifies the
signal and filters it to remove noise from the signal. As the
adjustment assembly dial screw rotates, the potentiometer's
resistance changes as the position of the wiper assembly along the
resister changes, which in turn changes the sensor electrical
output circuit's output voltage. Because the output voltage is
proportional to the resistance of the potentiometer, it is also
proportional to the desired preset torque value being selected by
the user.
[0042] FIG. 9 illustrates a functional block diagram of the
electronics unit of a torque wrench in accordance with one
embodiment of the present invention. The analog electrical signal
64 from sensor electrical circuit 101 is converted to an equivalent
digital value by an analog to digital converter 91 (FIG. 10) and is
then fed to a microcontroller 102. A control algorithm 104 (FIG.
10) residing in microcontroller 102 converts the equivalent digital
value into an equivalent preset torque value. A conversion table
may be stored in memory accessible by microcontroller 102 for this
purpose. A unit conversion algorithm converts the preset torque
value to the units (inch-pound, foot-pound, Newton-meter or kg-cm)
selected by the user via unit selector switch 66b (FIG. 1). The
choice of units can be increased to cover all possible units by
changing the appropriate algorithms. An electrical signal 69 for
the resulting digital torque value is then sent to a liquid crystal
display driver 68 and the preset torque value is displayed on
liquid crystal display 54 while the user sets the desired preset
torque value.
[0043] After the desired preset torque value is selected, the user
presses angle mode selector button 66c to enter the angle mode of
the torque wrench so that a desired preset angle value may be
selected. As best seen in FIGS. 12A through 12C, an angle mode
indicator 97 displays "Target Ang" when the user selects the angle
mode. The user now utilizes increment/decrement buttons 65a and 65b
to select the preset angle value which is displayed on numeric
display 60. After the preset angle value is set, the user presses
angle mode selector button 66c to place the wrench back in the
torque mode and the preset torque value is once again displayed in
numeric display 60.
[0044] Referring again to FIG. 9, as the user applies torque to the
wrench, and thereby the fastener, once the preset torque value has
been applied to the fastener and the torque wrench subsequently
"trips", as discussed in greater below, the user transitions the
torque wrench from a first mode, or torque mode, to a second mode,
or angle mode. As part of the shift in modes, microcontroller 102
sends an electrical signal 69 to digital display 54, causing it to
display "Ang" in angle mode indicator 77 and the current
accumulated angle value on numeric display 60 of the fastener as a
numeric value, as shown in FIG. 12C. In the present embodiment, the
user depresses angle mode selector button 66c in order to change
the operating mode from the torque mode to the angle mode and
switch digital display 54 from displaying the preset torque value
to displaying the accumulated angle value.
[0045] When mechanical torque wrench 10 is used to measure angular
rotation, gyroscopic sensor 27 senses the rotation of the
mechanical torque wrench and sends an analog electrical signal 61
that varies in voltage proportionally to the rate of rotation to a
gyroscopic signal conditioning unit 63 that amplifies the signal
and filters it to remove noise from the signal. Gyroscope signal
conditioning unit 63 outputs an amplified and conditioned analog
electrical signal 65 to microcontroller 102 that converts
electrical signal 65 to an equivalent angular value in degrees and
adjusts for any offset of the signal. Adjusting for the offset of
the signal increases the accuracy of the wrench by compensating the
signal for any reading that may be present before the wrench is
actually rotated. Microcontroller 102 sends an electrical signal
69, including the current accumulated angle value to digital
display 54, via LCD driver circuit 68. Preferably, digital display
54 displays the current accumulated angle value in the form of both
a bar graph display 71 and a numeric value display 60 during the
rotation of the wrench up to a preset target accumulated angle
value, as shown in FIG. 12C.
[0046] Referring additionally to FIGS. 10, microcontroller 102
converts analog electrical signal 65 to an equivalent angle value
in degrees. Upon receiving analog electrical signal 65,
microcontroller 102 converts analog electrical signal 65 to digital
data points using an analog-to-digital converter 91. As well,
microcontroller 102 adjusts electrical signal 65 for any offset of
the signal. When mechanical torque wrench 10 is powered on, it is
possible that gyroscopic sensor 27 will produce an electrical
signal 61 even though mechanical torque wrench 10 is not being
rotated. As such, microcontroller 102 determines the value of the
no-load electrical signal 65 when the torque wrench is powered on
and subtracts this value from all subsequent electrical signals 65
received from gyroscopic sensor 27 during torquing operations.
Microcontroller 102 can adjust the received electrical signal 65
either prior to, or after, its conversion to a plurality of digital
data points with the analog-to-digital converter. Since the
conditions under which mechanical torque wrench 10 are used can
differ, microcontroller 102 determines the magnitude of the no-load
electrical signal 65 each time the mechanical torque wrench 10 is
powered on and applies that value to that series of torquing
operations that occur prior to powering off the mechanical torque
wrench 10.
[0047] In one embodiment, microcontroller 102 utilizes a moving
window digital filtering algorithm to convert the digital data
points from analog-to-digital converter 91 into a plurality of
equivalent digital values that it then uses to determine the
accumulated angular rotation being applied with the mechanical
torque wrench 10, as discussed in greater detail below. In the
present example, microcontroller 102 samples one thousand digital
data points per second and uses a moving sample window of 10
milliseconds. As the mechanical torque wrench rotates,
microcontroller 102 averages the first ten digital data points, one
taken each millisecond, thereby producing a first equivalent
digital value at time t=0.01 seconds, wherein t=0.0 seconds marks
the initiation of rotation of the torque wrench. At time t=0.011
seconds, microcontroller 102 averages the digital data points taken
between times t=0.002 and t=0.011 seconds, thereby producing a
second equivalent digital value. At time t=0.012 seconds,
microcontroller 102 averages the digital data points taken between
times t=0.003 seconds and t=0.012 seconds, thereby producing a
third equivalent digital value. This continues such that an
equivalent digital value is provided every millisecond until the
mechanical torque wrench 10 is no longer being rotated.
Microcontroller 102 utilizes these equivalent digital values and a
numerical integration method, as discussed below with regard to
FIG. 11, to determine the accumulated angle value being applied by
the mechanical torque wrench 10.
[0048] FIGS. 11A and 11B are flow charts of the algorithm utilized
by mechanical torque wrench 10 to determine accumulated angle
values. More specifically, FIG. 11A is a flow chart of the main
program of microcontroller 102, and FIG. 11B is a flow chart of an
interrupt routine service program that the provides averaged values
of the equivalent digital values discussed above with regard to the
digital filtering algorithm. As shown, when the mechanical torque
wrench 10 is powered on, the electronics configuration is
initialized, and microcontroller 102 determines the offset signal
of gyroscopic sensor 27, as previously discussed. Upon entering the
angle mode, microcontroller 102 performs an infinite loop operation
as long as the torque wrench is not powered off. Upon entering the
loop, microcontroller 102 initiates a timing sequence that is
related to the digital filtering algorithm discussed above. In the
present embodiment, the timing sequence comprises a 10 millisecond
window over which the equivalent digital values provided by the
digital filtering algorithm are averaged such that an average
equivalent digital value is provided for numerical integration
every 10 milliseconds rather than every millisecond. For example,
first average equivalent digital value of the first through tenth
equivalent digital values is provided for numerical integration
rather than the 10 individual values. As such, the next value
provided is a second average equivalent digital value of the
eleventh through twentieth equivalent digital values. At the end of
each 10 millisecond window, the timing sequence interrupts the main
program and provides the average equivalent digital value, which
microcontroller 102 then uses to calculate the angular velocity of
mechanical torque wrench 10 over that 10 millisecond window by
retrieving a corresponding calibration constant that is stored in
flash memory. Each calibration constant corresponds to an angular
velocity value that is previously determined during the calibration
of the torque wrench, as discussed below.
[0049] Microcontroller 102 performs a numerical integration with
the average angular velocity values determined for each 10
millisecond period to determine the accumulated angle value through
which the mechanical torque wrench is rotated, and subsequently,
the fastener as well. Microcontroller 102 sends an electrical
signal including the current accumulated angle value to the digital
display. In the present embodiment of the torque wrench,
microcontroller 102 performs the numerical integration in
accordance with the equation:
.theta. = i = 0 n .omega. i .DELTA. t ##EQU00001##
where, (.theta.) is the accumulated angle value, (.omega.) is the
calibration constant retrieved by the microcontroller 102 in
response to receiving the (i.sup.th) average equivalent digital
value, and .DELTA.t is the preferred sample period of 10
milliseconds.
[0050] Note, in alternate embodiments of the mechanical torque
wrench, the digital filtering algorithm does not utilize the moving
window method of averaging to determine the individual equivalent
digital values. Rather, the digital filtering algorithm determines
an independent equivalent digital value each millisecond that
corresponds to the electrical signal produced by gyroscopic sensor
27, beginning at time t=0.001. The digital filtering algorithm then
averages the individual equivalent digital values over a selected
window of time, that being 10 milliseconds in the present example,
and provides the average equivalent digital value to
microcontroller 102 for use in the previously discussed numerical
integration method. In yet another alternate embodiment of the
mechanical torque wrench, no averaging feature is utilized by the
digital filtering algorithm in providing equivalent digital values.
Rather, the digital filtering algorithm simply produces an
equivalent digital value at the end of a selected window of time,
that being 10 milliseconds in the present example, and provides
this equivalent digital value to microcontroller 102 for use in the
previously discussed numerical integration method. These
embodiments may be desirable when a lesser degree of accuracy from
the mechanical torque wrench is acceptable.
[0051] Preferably, after assembly, each mechanical torque wrench 10
is calibrated in order to derive the previously discussed
calibration constants that are stored in flash memory. The
mechanical torque wrench is rotated at a plurality of known angular
velocities that would be expected to be encountered during normal
operation of the mechanical torque wrench. The equivalent digital
value produced at each known angular velocity is measured and
recorded. A curve is fit to these data points that allows the
determination of the angular rotational value, or calibration
constant, for each received equivalent digital value.
[0052] Microcontroller 102 generates alarm signals in the form of
audio signals and light displays of appropriate color once it is
determined that the current accumulated angle value of the fastener
is within a pre-selected range of the preset target accumulated
angle value. As previously discussed, once the mechanical torque
wrench trips at the preset torque value, the user manually switches
the torque wrench and digital display 54 from the torque mode to
the angle mode such that it displays accumulated angle values
rather than the preset torque values.
[0053] FIGS. 12A and 12B show detailed views of preferred
embodiments of digital displays 54a and 54b, respectively. The LCD
units include accumulated angle indicator 71, a four digit numeric
display 60, an indication of units selected 62 (foot-pound,
inch-pound, and Newton-meter), a torque direction indicator 93
(clockwise (CW) by default and counter-clockwise (CCW) if
selected), a battery level indicator 95, an angle mode indicator 97
and an error (Err) indicator 89. As shown, accumulated angle
indicator 71 is in the form of a bar graph. The bar graph is shown
in two embodiments, horizontal 54a (FIG. 12A) and vertical 54b
(FIG. 12B). In either case, preferably, the bar graph includes a
total of ten segments 79 and a frame 81 that encompasses all ten
segments 79. Frame 81 is filled by the ten segments when the preset
accumulated angle value input by the user, as discussed below with
regard to FIGS. 13A and 13B, is reached. At other times, frame 81
is only partially filled with segments 79, and therefore gives a
graphical display of approximately how much accumulated angular
rotation the fastener has undergone and how much more needs to
occur. Note, prior to the user manually selecting the angle mode of
the torque wrench, none of the segments will be present in frame
81, as shown in digital displays 54a and 54b.
[0054] As shown, two small arrows 83 are located on opposing sides
of the eighth segment. Arrows 83 are graphical indicators to the
user that accumulated angle measurement is above 75% of the preset
value. Each segment 79 within frame 81 represents 10% of the preset
angle value, starting from the left or bottom of each bar graph,
respectively. For example, if only the first two of segments 79 are
displayed, the current angle value is above 15% and below 24% of
the preset angle value, and is therefore approximately 20% of the
preset angle value. Simultaneously, digital display 54a/54b also
displays the accumulated angle value applied up until that time in
numeric display 60, as discussed in greater detail below.
[0055] Once the target preset torque value has been reached and the
angle mode of the torque wrench is entered by the user depressing
angle mode selector button 66c, numeric display 60 displays the
accumulated angular rotation of the torque wrench, rather than the
preset target torque value, and angle mode indicator 97 shows "Ang"
to indicate the wrench is in the angle mode, as best seen in FIG.
12C. When continuing to rotate the fastener, the user may, rather
than focusing on four digit numeric display 60, view the bar graph
of current accumulated angle indicator 71 until the applied
accumulated angle value reaches approximately 75% to 80% of the
preset target accumulated angle value, depending on the user's
comfort level when approaching the preset value. At this point, the
user may change focus to numeric display 60 for a precise
indication of the current accumulated angle through which the
fastener has been rotated as the preset target value is approached.
Numeric display 60 shows the accumulated angle value to which the
fastener has been subjected. As such, if the user has "backed off"
during the application of rotation, such as during ratcheting
operations, the value indicated on numeric display 60 will not
change until the mechanical torque wrench senses further rotation
of the fastener. Display device 54c allows the user to know both
how much rotation the fastener has undergone and how much more
rotation needs to occur before reaching the target preset
accumulated angle value.
[0056] FIGS. 13A and 13B illustrate a flow chart 100 of the
algorithm used with the electronics unit. Prior to initiating
torquing operations, the input device is used to set a preset
target torque value into the mechanical torque wrench that equals
the maximum desired torque to be applied to the fastener during the
torquing mode. As well, after inputting the preset target torque
value, the user selects the target angle mode, as discussed above,
and inputs a preset target accumulated angle value into the
mechanical torque wrench that equals the maximum desired angular
rotation to be applied to the fastener subsequent to reaching the
preset target torque value. After the preset target accumulated
angle value is entered, the user presses angle mode selector button
66c and the mechanical torque wrench reverts to the torquing mode,
and digital display 54 displays the preset target torque value in
numeric display 60 (FIGS. 12A and 12B).
[0057] Referring additionally to FIG. 9, as torque is applied,
microcontroller 102 (for example, Model No. ADuC843 manufactured by
Analog Devices, Inc.) continues to receive and read a signal
conditioned analog electrical signal 64 from resistive element
signal conditioning circuit 62, convert the analog electrical
signal to an equivalent digital number, convert the digital number
to an equivalent preset torque value corresponding to the user
selected units, send electrical signal commands 69 to LCD driver
circuit 68 (Model No. HT1621 manufactured by Holtek Semiconductors,
Inc., Taipei, Taiwan) to generate appropriate signals to digital
display unit 54 for displaying the preset torque value in numeric
display 60.
[0058] The amount of torque applied to the fastener increases until
clicker mechanism 26 (FIG. 2) trips such that bar 20 pivots
relative to wrench body 14, thereby striking the wrench body, as
previously discussed. Once the preset torque value is reached, the
user enters the angle mode by pressing angle mode selector button
66c. As shown in FIG. 10, as the user begins to rotate the
mechanical torque wrench, microcontroller 102 receives and reads a
signal conditioned analog electrical signal 61 (as previously
discussed with regard to FIG. 9) from gyroscopic sensor 27,
converts the analog electrical signal to an equivalent digital
number, and converts the digital number to an equivalent current
angle value. Simultaneously, microcontroller 102 determines whether
the signal conditioned analog signal from gyroscopic sensor 27 is
positive (+) or negative (-) in order to determine whether or not
to measure and accumulate angular rotation. More specifically,
gyroscopic sensor 27 generates either a positive or negative signal
based on the direction of rotation (either CW or CCW) of the torque
wrench. As such, dependent upon whether the user has selected to
apply torque in the CW or CCW direction, microcontroller 102 can
determine when torque is being applied to the fastener and thereby
accumulate angular rotation, or determine that only ratcheting is
occurring and not accumulate angular rotation.
[0059] Microcontroller 102 also determines whether the current
accumulated angle value is equal to or greater than the preset
target accumulated angle value. If the current accumulated angle
value has not yet reached the target value, microcontroller 102
sends electrical signal commands 69 to LCD driver circuit 68 to
generate appropriate signals to digital display unit for updating
the number of segments 79 shown in current accumulated angle
indicator 71 and the current accumulated angle value shown in
numeric display 60.
[0060] As well, microcontroller 102 switches green 56a, yellow 56b,
and red 56c LEDs on or off depending on the current accumulated
angle value applied to the fastener up until that time. Preferably,
microcontroller 102 maintains green LED 56a on as long as the
current accumulated angle value is below 85% of the preset target
accumulated angle value and switches it off once the current
accumulated angle reaches 85% of the preset target accumulated
angle value. Microcontroller 102 switches yellow LED 56b on for
current accumulated angle values greater than 85% but less than 96%
of the preset target accumulated angle value. Microcontroller 102
switches red LED 56c on once the current accumulated angle value
reaches 96% of the preset target accumulated angle value and stays
on thereafter. Once the current torque value reaches the preset
target accumulated angle value, or is within a user selected range,
microcontroller 102 generates electrical signals to generate an
alarm sound on annunciator 47. At this point, the user ceases to
rotate the mechanical torque wrench, and numeric display 60
alternately flashes both the preset torque value and the final
accumulated angle value to which the fastener was subjected. Note,
however, it may be possible to achieve the preset target
accumulated angle value without having to use the ratcheting
feature of the mechanical torque wrench, i.e., the desired rotation
of the fastener is achieved with a single rotational stroke of the
torque wrench. In many applications, the fastener will need to be
rotated by using multiple ratcheting cycles. The selection of
percentage ranges for each color may be programmed, and the
percentages at which the LEDs are switched on or off can be changed
to suit the specific application.
[0061] The torque wrench continues to accumulate angle either until
the wrench is powered off or until the user depresses the angle
mode selector button 66c twice in rapid succession (thereby ending
the while loop indicated in FIG. 11A). Thus, the wrench may be
considered to accumulate angle during a period that is
predetermined by those conditions.
[0062] The algorithm also keeps track of the activity of the torque
wrench. If the wrench is inactive for a predetermined period of
time, the electronics unit shuts off the power to save battery
life. Preferably, a predetermined period of three minutes is used.
Regardless of whether the unit is switched off by manually pressing
the power button or due to an inactivity-triggered auto shutoff,
the microcontroller saves the unit selected in non-volatile memory
(flash memory in the preferred embodiments). This feature allows
the electronic unit to come on and display the last preset torque
value and selected unit.
[0063] The embodiments of the mechanisms for converting the
mechanical rotary dialing motion into an equivalent electrical
signal described herein are for illustration purposes only. It is
envisioned that other embodiments may also use optical, magnetic,
or capacitance based mechanisms as position sensors for the dial
screw rather than the resistance-based mechanism discussed above.
For example, magnetic sensors such as magnetostriction rods with
ring wipers can be used. Similarly, optical scales and laser diode
readers can be used, as can capacitance sensors having two sliding
grid patterns with one stationary and the other movable to change
the capacitance. Furthermore, the mechanical rotary motion of a
thumb wheel used in split beam type mechanical torque wrenches
falls within the scope of this invention. No matter what mechanism
is used to generate the rotary motion, the methodology needed to
convert the rotary motion to an equivalent electrical signal does
not change from what is described in this invention. These and
other like mechanisms that can be used to convert a mechanical
rotary motion into an equivalent electrical signal are within the
scope of this invention.
[0064] While one or more preferred embodiments of the invention are
described above, it should be appreciated by those skilled in the
art that various modifications and variations can be made in the
present invention without departing from the scope and spirit
thereof. It is intended that the present invention cover such
modifications and variations as come within the scope and spirit of
the appended claims and their equivalents.
* * * * *